Walter Shapiro looks at the story of Mitt Romney’s dog Seamus “heroically riding for 12 hours in a dog carrier atop the family’s station wagon during a 1983 vacation to Canada” and says it has less to do with his treatment of animals than it does his treatment of people.

“What gives the Seamus story legs (four) is the inadvertent glimpse it offers of Romney’s rigidity. For all the natural parental annoyance with the constant are-we-there-yet demands and the bodily needs of five boys on the trek to Canada, it is a rare father who would so zealously limit bathroom and food stops. Remember: The Romneys were not exactly desperate refugees racing to get across the Canadian border before they were stopped by the authorities. They were an affluent American family on vacation, but with all the spontaneous joy of an automotive assembly line. Seamus was collateral damage. What matters is the suck-it-up discipline that Mitt Romney tried to impose on his family.”

“People are not cyborgs — they have human needs, including a propensity for rest stops and, in politics, healthy egos. But an awareness of these personal factors does not seem to be part of the Romney repertoire.”

Nate Silver: “At the betting market Intrade, Mr. Santorum is now given just a 1.5 percent chance of winning the nomination — lower than the combined total for a series of dark-horse figures like Jeb Bush, Sarah Palin and Chris Christie, who together have about a 3 percent chance. The race will continue on until Mr. Romney clinches or everyone else quits, but the only real question is whether Mr. Romney could somehow beat himself.”

Paul Begala: “The biggest reason negative ads are so ubiquitous in politics, but much less common in commercial advertising, is this: elections present a mutually exclusive choice. It is legal to buy a can of Coke and a can of Pepsi on the same day, but you can’t vote for Obama and Romney in the same election. That mutual exclusivity pushes campaigns to frame the choice more sharply. Imagine if we had Cola Day once every four years — and you were stuck with your choice for those four years. Coke would say Pepsi makes you fat; Pepsi would counterattack that Coke makes you impotent. And they’d go downhill from there.”

“So the next time a public moralist starts lamenting the role of negative advertising in our political system, just explain that it’s an outgrowth of the stakes involved. As the old saying has it, politics ain’t beanbag — and a political campaign isn’t selling soft drinks. The outcome matters — and influencing it is worth every negative word or image a candidate and his team can muster.”

NBC News highlights a RNC rule stipulating that candidates seeking the nomination must have won a plurality of votes in at least five states to have their name presented for the GOP nomination.

Said RNC Chairman Reince Preibus: “It’s an important rule. So when these candidates are adding up their delegates or when people out there have a particular issue that they would like to move at the convention, they had better make sure they at least have a plurality of five states to make these things happen.”

Newt Gingrich has only won two primaries so far — South Carolina and Georgia.

A Quinnipiac poll finds Virginia Gov. Bob McDonnell’s (R) approval rate at 53% to 32% — a drop of 13 points in his net approval rate since last month.

The change is almost entirely the result of a shift by women that occured during the state legislature’s debate over a new law that requires women seeking an abortion to undergo an ultrasound examination.

First Read: “One, Obama’s fundraising and cash on hand is on par — more or less — with Bush’s numbers in ’04 (which is surprising given what many, including us, thought he was capable of raising at the beginning of this race)… Two, Romney’s burn rate is over 100% (which might explain why the Super PAC, and not the campaign, is airing ads in post-Illinois races)… Three, the pro-Santorum Super PAC has just $365,000 in the bank (Foster Friess, you have a call on Line 2)… Four, Gingrich now has more in debt ($1.55 million) than cash on hand ($1.54 million)… And five, the pro-Obama Super PAC Priorities USA continues to be a flop, with it raising just $2 million (half of which came from Bill Maher).”

“By the way, don’t overlook the spending numbers for the campaigns. It’s where you learn the philosophies of the campaign. Obama’s campaign is putting a LARGE emphasis (read: money) online. A large chunk of the February spending was devoted to online advertising. Also, do note that the Obama campaign continues to keep overall STAFF salaries down, at least compared to what other campaigns pay, including Romney. In fact, Romney has at least five staffers who make more than Obama’s campaign manager.”

President Obama will not recognize the two-year anniversary of his signing of the health care law — “which takes place days before the Supreme Court offers a decision on the constitutionality of his signature legislative achievement,” The Hill reports.

“Senior administration officials said on Tuesday that Obama will not be offering a vigorous public defense of the law, holding events or even making public remarks in the lead-up to the Supreme Court case. Obama will instead leave arguments to the Justice Department, which begins defending the law on Monday. Likewise, Obama is not expected to hold an event around the two-year anniversary on Friday, said officials who labeled it a faux milestone and off the radar of most Americans.”

Mark Halperin: “Romney’s Illinois win could be the beginning of the end of the Republican nomination fight. In order to get there, he faces two challenges: He’ll have to convince on-the-sidelines Republicans to endorse his candidacy, contribute to his campaign, and muscle Rick Santorum and Newt Gingrich out of the race. And he’ll also have to persuade the media to reflect the reality that Romney is the only candidate who can win… Santorum probably has one more chance to change the paradigm with a win in Wisconsin on April 3, after an expected victory in Louisiana on Saturday.”

Fred Barnes: “Mitt Romney is close to finishing off his rivals for the Republican presidential nomination, talk of a brokered GOP convention in August, and the prospect of a new candidate suddenly entering the contest.”

First Read: “Despite what some are saying, however, the race isn’t over — at least not yet: The GOP primary contest moves on to Louisiana, where Santorum is favored. And then, on April 3, it heads to DC, Maryland, and Wisconsin. If Romney pulls off the upset in Louisiana and/or sweeps the April 3 contests (especially Wisconsin), then it will be fair to conclude the race is over.”

“It’s a form of welfare. You know, you’re having the taxpayers pay to take care of somebody and I’m an ordinary citizen and I would think I should pay for my own protection and it costs, I think, more than $50,000 a day to protect those individuals. It’s a lot of money.”

“Watching Mitt Romney’s victory speech in Illinois didn’t reassure me about his chances against President Obama. (Watch it yourself to see if I’m being unfair.) Romney’s remarks consisted basically of the claim that the business of America is business, that he’s a businessman who understands business, and that we need ‘economic freedom’ not for the sake of freedom but to allow business to fuel the economy. It’s true that Romney will have plenty of time to improve for the general election, if, as seems likely (but still not inevitable!), he wins the nomination. But if he sticks with this core message, we’d better hope Republicans and independents are really determined to get rid of Barack Obama.”